This invention relates to a sintered metal body with at least one toothing, the toothing being formed in a blank by metal forming with or without pre-toothing.
In DE-PS No. 2659733 a sintered metal body with at least one toothing is described, the toothing being formed in a blank by metal forming with or without pre-toothing. According to this process, toothed gears are manufactured with a profile shift which changes continuously and regularly from one front face of the toothing to the other front face with a beveled enveloped surface of the toothing.
For this purpose, a master gear is made by a cutting process, then from the master gear, using an image-forming manufacturing process, a die is manufactured. The toothing of a gear is produced by a shaping process in the die under heat in which a predetermined temperature at the end of the shaping process is strictly adhered to, and in which the contraction of and the modular change in the toothing upon the cooling down of the workpiece from the prescribed final temperature are compensated for by corresponding changes of the dimensions of the master gear. As a result, the toothed gear produced in the die is calibrated with nominal dimensions using a calibration die which is manufactured by an image-forming manufacturing process from a second master gear which is made by a cutting process. In the course of the manufacture of the toothed gear by a sintering process, the contraction of and the modular change in the toothing during sintering and cooling down of the workpiece are corrected by corresponding changes in the dimensions of the master gear.
According to the process described above, including forging a toothed gear using an initial master gear and a die made from the initial master gear, considering the contraction of and the modular change in the toothing, and calibrating the toothed gear in a calibrating die made from a second master gear, which deviates from the initial master gear it is possible to manufacture gears with a cylindrical rolled surface for gearing with a high degree of precision when the dies have good tool-life. This process involves very high costs of production, and is likely to be employed only in special cases.
The U.S. patent to Dunn et al, U.S. Pat. No. 3,772,935, describes a process for forming a toothing in a blank made of sintered metal material by metal forming (see in particular FIGS. 5 and 6). This process uses a type of stamping tool to press the material into a form in order to produce the workpiece. The teeth require a finish machining process, such as, grinding or cutting.
According to a procedure described in "Machine Design", 1972, pp 72-76, a final toothing is achieved from a pre-toothed sintered metal blank by one or more metal forming processes.